Handbook of Meat Processing

Physical Sensors for Quality Control during Processing 449

α-dispersion (counterion effect)

permittivity β-dispersion (maxwell-wagner effect)

γ-dispersion (dipolar effect)

conductivity

frequency (Hz)

1,E

+00

1,E–01

1,E+00

1,E+01

1,E+02

1,E+03

1,E+04

1,E+05

1,E+06

1,E+07

1,E+08

1,E

+01

1,E

+02

1,E

+03

1,E

+04

1,E

+05

1,E

+06

1,E

+07

1,E

+08

1,E

+09

1,E

+10

1,E

+11

conductivity (S/m) Permittivity (dimensionless)

Figure 25.7. Dispersions of meat tissue with fi bers in transversal direction (Castro - Gir á ldez et al. 2007a ).

tion of the intensity of the electric fi eld by the
passive cell membrane capacitance, intracel-
lular organelle membranes, and protein mol-
ecules. At low frequency, the dispersion
produced is the counter - ion effect, where the
electric fi eld produces changes in the trans-
port channels of the cell membrane to acti-
vate the anion infl ow through the membrane,
changing the polarity of the extra - and intra-
cellular liquid phase of cells (Grimnes and
Gr ø ttem - Martinsen 2008 ).
In assessing meat quality, some authors
used bioimpedance spectroscopy to separate
the PSE (pale, soft, exudative) meat, DFD
(dark, fi rm, dry) meat, and RFN (red, fi rm,
nonexudative) meat (Swatland 1999 ; Castro -
Gir á ldez et al. 2007a ). Castro - Gir á ldez et al.
(2007a) published that an amount of ATP
variation exists in storage for each type of
pork meat and related the ion activity of
ATP with the ionic dispersion in the dielec-
tric spectra. Figure 25.7 shows the three dis-
persions of normal pork meat and the electric
conductivity variation. Castro - Gir á ldez et al.
(2007a) showed the variation of the dielectric
spectra before and after rigor mortis, devel-

oping a method to determine the freshness

of pork meat using the β - dispersion measure,

because Maxwell - Wagner dispersion is

affected by the structural protein ’ s degrada-

tion throughout meat maturation. The inter-

action of the protein degradation in the

β - dispersion has been used to determine the

tenderness of pork meat (Byrne et al. 2000 )

and bovine meat (Lepetit et al. 2002 ).

Some chemical compounds or group of

compounds have been related to the dielec-

tric properties as fat content, analyzed with

electrodes inserted in the muscle before rigor

mortis, in reference to the a - dispersion varia-

tion (Madsen et al. 1999 ). In salted and cured

pork meat, some authors have developed

methods to control the salting level and mois-

ture. Castro - Gir á ldez et al. (2007b, c) explain

a thermodynamic model coupled with dielec-

tric measures in the range of the g - dispersion

to control the shear out of salt and water, and

establish the water adsorbed in meat matrix

and the salt involved in the protein meat

degradation. Some commercial sensors

have been developed recently to control phy-

sical and chemical properties, such as the